Dietzen, 35, a cast member of “NCIS” since 2004, was born in Barrington, Ill., and grew up in Boulder, Colo., where at age 8 he made his acting debut as an evil elf in a Christmas play. He and Abby Miller wrote, produced and star in “Congratulations,” which explores modern marriage and is now playing at film festivals. “It’s pretty meaningful for a lot of people of my generation: people waiting longer to get married,” he says. The father of children, ages 5 and 3, enjoys hiking with his wife, golfing with “NCIS” co-star David McCallum, and playing softball.